Measuring or detecting device



Nov. 18, 1930. w. J. STALLAN 1,732,151

MEASURING-OR DETECTING DEVICE Filed Dec. 9, .1929

1.5 16 i 4/. J/i/fio recordingm .1 Other objects will be explainedhereinafter,

Patented Nov. 18, 1930 j. UNITED STATES PATENT oFFIc -f wILLI'AM'aAMns s'raLLAN, on CAMBRIDGE, Enetanmnssmnoa To CAMBRIDGE IN; STRUMENT coMranYgnnumnn, or onnon, ENGLAND, A CORPORATION OF GREAT BRITAIN.

l Application filediD'ecemb er-g, 1929, seal No.

;10fple, recording vibrographs are employed, for

' determining the effects ofprearrangedexplosions. 1 These explosions-are caused to make in'dlcations or records that enable one to ascertain the probability of thefpresencef 15 of oil orminerals. -As the basic movements impressed upon' the moving mass of the .vibrographby the explosion are of extremely I small order, it is necessary to magnify them considerably to permit their inspection .or

object of the present invention,there-, fore',,is.to provide a new-and improved 1nzst rumentfor magnifying very small movementsof the above-described character.

and'will be particularly pointed outin appended claims. 4 r (I Withthe aboveends in View, a'feature of theinvention,though the invention is not the ' limited thereto, resides in the use of a disc,

mounted upon a spindleand rotatable about the axis thereof, in combination with amem- I ber connected, at oneend, to a point of the moving part ofjthe movement which is to v be measured or detected and,at theother end, to apoint of the disc. Preferably,the said point of the disc lies, throughout its rangeof movement, outside of the plane common to'the axis of'the disc and the moving $0 point. -.A mirror-fixedto the spindle of the disc is employed to reflectlight rays from a source, thearrangement constituting an optical-lever', system for further magnifying the movement, or the record of. the movement,

.45 ofthe moving point.

The invention will now be explainedin connection with the accompanying drawings,

, in which Fig. 1 is a diagrammatic view of a vibrograph or seismograph embodying the 5 I present invention in its preferred form; and

" j MEAsURINGoR DETECTING DEVICE. a

412,671, and in Grea Britain has 6, 1929.

Fig. 2 is an enlarged detail of a portion of I the mechanism shown in Fig. 1.

J The moving point, the .very small move-j mentof which is to be detected, mayxhe assumed to be at A, upona moving member-1.

Themember 1 maytypify any moving part,

such as a vibrograph lever 1, pivoted at B upon a fulcrum 2, and weighted at. the point C with a weight 3. The lever 1 may be spring supported at 4 and5tocompensate for the eifect of gravity upon the weight 3.. In the illustrated embodiment of the invention,

therefore, the point Ai's assumed to be subjected to slight vertical movements, but it I .55 7 so limited, but is so disclosed for illustrative .purpose s'purely. I M r 7 connects themoving point I A on the lever ,1 with a point D on a hori zontall-y-disposed=disc 10. r A vertically-diswill be understood thatthe'invention is not Aro'd or link posed spindle14 joins the disc 10 at its center and its ends rest in vertica-lly disposed pivot bearings 8 and 9. 'A hairspring 12 {is attached at one-end 17 to the spindle 14 and at its other end toafixed point 18 ofthe instrument- The point '18 may conveniently'be located upon the pivot bearing 8.- Thejhair spring thus maintains the link or rod 7 yieldingly'in'aposition as close as possible to the plane containing the point A and the spindle 14. When the lever 1 moves down ward, however, in res ponse to shock, the link or rod 7 will also be forced downward, inopposition to the force exerted by the spring 12, causing the disc to turn or rock about the:

axis of the spindle 14 in the direction of the arrow of Fig. 2. Upon the return of the lever 1 to its normal position, the disc 10will similarly bereturned to its original position.

It will beunderstood, of course, that the disc 10 does notneed to be horizontal, nor'the spindle 14vertical, the disclosed embodiment of the invention being for illustrative purposes only.

This turning movement of the disc 10 is many times as great as the very slight movement;of the point A on the lever 1. The movement may, however, be magnified many times further'by means of an optical-lever arrangement, such as a mirror 11, fixed to V the spindle 14, for reflecting a beam of light I of the instrument.

from a light source 15 to a scale, photographic film, or other recording device 16.

The following analysis will indicate the degree of magnification of the movement of the moving point A:

Let L=the length of the rod or link 7, be-

It will be noted that'L'and r are constants For practical purposes, the same may be said of a. As the point A moves up and down in response'to shocks upon the instrument, its vertical distance-z above the point 0 is variable, and this causes the angle 9 to vary :also.

Let the center of coordinates O be taken at the center of the disc 10; the axis of coordinates OX as the. horizontal line in the the vertical axis of the spindle14. f I r Then the coordinates of the pointA are a, 0, z) and those of the point D are (recs 9,? sin 9,0). It follows that the square ofthe length of the rod orlink 7 is p L =("r"cos9+a)?+r sin 9+2? In order to find what effect, d9, is produced upon 9 by reason of a small change de in 2, this expression may be differentiated with respect to a i (1' cosEH-a) r sin 9036+? sin 9 cos 9.0l9+-z,dz=0,

arsin 6.d9+z.dz=0.

To a first approximation, 2 and L are equal. Hence,

arsin 9 From this, it'readil'y appears that small movements dzof the point A will be magnified into angular movements (Z6 of the disc 10 in proportion to the length L and iiiversely in proportion to the lengths or and r tice, a and 7 may be of the order of 10 and 1 I meters.

millimeters each and L as much as 7 centi- 'In view of the presence, at the point C, of

' the weight '3, the full effect of the shock will not be communicated to the point A. It will make its effect felt in the proportion i BC This ratio may be, say, from 2 to 10.

To determine what further magnifying effeet is introduced by the source of light 15, the mirror 11 and the scale 16, the above expression should be multiplied by tW-icethe distance of the scale 16 from the mirror 11. This distance may, in practice, he one or' two meters.

Modifications will occurto persons skilled in the art, and all such are considered to fall within the spirit and scope of'the invention, as defined in the appended claims.

What is claimed is: a

1. An instrument for detecting very small movements of a point having, in combination,

means connecting the point with another tecting the movement of the second-named point.

planeof the axis of the spindle 14 and the point A; the axis of coordinates O'Y as horizontal and normal to OK, and the axis of co-. ordinates OZ as -path in a pl anedisposed' at an angle to the path of movement of the first-named point,

and means 'for detecting themovemen't of the said other point.

3. An instrument for detectingvery small movements of a lever about'a pivot having, in combination, a link connectmg a point of the lever with a point of a rocking disc the plane of which is disposed at an angle to the path of movement of the point of the lever,-

gnd means for detecting the movement of the lsc.

4. 'An instrument for detecting very small movements of a point having, in combination, a link connecting the point with another point that is constrained to move along the arc of a circle, the said other point being outside of the plane common to the first named point and the normal to the circle through the center of the circle, and means for detecting the movement of the said other point.

5. An instrument for detecting very small movements'of a point having, in combination, a rocking disc, a link connectingthe point with a point of the disc, whereby movementsof the first-named point will be communicated to the disc, the said point of the disc being outside of the'plane common to the first-named point and the axis of the disc, and means for detecting the rocking movement of the disc. v

6. An instrument for detecting very small movements of a point having, in combination, a disc mounted on a spindle so as to be rotatable about the axis of the spindle, and a member connected by one end to the said moving point and by the other end to a point on the disc whiohlies outside the plane common 1 to the axis of the disc and to the said moving point.

In testimony whereof I have hereunto set my hand. 7

WILLIAM JAMES STALLAN.

so I 

